The only significant danger/side effect of the drug is in vaping CBD oils that were produced using a thinning agent, such as propylene glycol. When burned/vaped, propylene glycol produces formaldehyde, which is a known carcinogen. CBD oils produced by CO2 extraction are much safer and more pure than oils that were produced with liquid alcohol/thinning agents.
Other than that, most research has concluded that CBD is perfectly safe with no known side effects, though some users have reported drowsiness, lightheadedness, low blood pressure, and dry mouth. Also, some patients with Parkinson’s Disease have reported an increase in tremors.